JFZ90, no Regulatory Authority can prevent accidents happening or indeed poor designs slipping through the net. The point is of course to reduce them to a minimum. How many people die because of badly designed and built cars, given the millions that are built each year and the people (like me) who are then free to exhibit their lack of driving skills with them? It is especially important that when such an accident does happen that immediate and effective action is taken to prevent the next one due to the same fault. That requires an objective and professional Accident Investigation and strong regulatory enforcement of the required corrective action. Think of the Manchester 737 abandon T/O due to No.1 engine fire. Terrible loss of life due to the aircraft stopping cross wind with the fire then working its way into the cabin. The corrective action was profound and far ranging; new drills, smoke hoods, floor track lighting, fire retardant seating, etc. A lot of expense for all operators and no alternative. Then consider the RAF's accident investigation and preventative action in this case. I would suggest that it was not effective nor objective, indeed the Coroners Service seems to have been a more effective conduit for what was wrong (it was unairworthy) and what should be done (grounded until made airworthy). The RAF used to do that sort of thing once, indeed it did so when I was a sprog co-pilot on Hastings. Not anymore though it would seem.